[Octave-bug-tracker] [bug #31352] interp2 broken for non-quadratic matrices when using cubic interpolation

[Marco Caliari]

Follow-up Comment #2, bug #31352 (project octave):

Dear all,

here is my first rewrite of cubic interpolation in interp2. Comments:

1) it uses spline interpolation instead of the more simple bicubic (it allows
not equispaced meshgridded X and Y)
2) The function is still undocumented and without input checking.
3) Thorsten's patch https://savannah.gnu.org/bugs/download.php?file_id=21707
should be applied to spline
4) another patch should be applied to spline in order to manage in a default
way the case 

spline([0,1],[0,1])

5) issues 3) and 4) can be ignored if you use enough (> 3) points for X and
Y
6) I could reduce the code to standard bicubic (as ml) if X and Y are
equispaced (it is faster and the default in ml), i.e. I can rewrite the actual
bicubic.m in a more accurate and faster way.

Comments?

Marco

(file #21716, file #21717)
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Additional Item Attachment:

File name: newinterp2.m                   Size:0 KB
File name: testnewinterp2.m               Size:0 KB


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